The invention described herein is an imaging device that produces an intensity image from a transparent phase object. The image intensity at a point in the image plane is related to the component of the gradient of the phase retardation in a particular direction at a corresponding point in the object plane. The visual aspect of this image is similar to that of an object illuminated by directed, shallow glancing illumination.
The images produced are different from common alternative methods for imaging phase objects, such as Zernike's phase-contrast microscope (where intensities are proportional to the values of the retardation themselves), or interference microscopes (which produce phase contours), or interference and holographic devices (where darkening occurs at points where there is a rapid variation of phase).